The present invention relates to communications between mobile stations and base stations in a wireless network, and more particularly to broadcast/multicast communications in the wireless network.
Transmission of multimedia data, such as video, has become more prevalent recently. For example, users desire to receive broadcast communications and to send and receive video data on their mobile stations, e.g., cell phones, PDAs, PCs, etc. Multimedia data often requires more bandwidth than other types of data, such as voice communications. However, due to bandwidth limitations, the growth in the transmission of multimedia data presents a problem for wireless networks.
Transmissions in wireless networks typically use unicast, multicast, or broadcast communications. Unicast generally refers to communications over a network between one sender and one receiver. Multicasting generally refers to transmissions to users/devices that have joined a particular multicast group. Broadcasting in a network generally refers to sending information to all of the users on the network.
Under a unicast approach, each user in a wireless network has his/her own connection profile and is treated separately. In this environment, multiple users cannot share a common air interface channel due to varying quality of service (QoS) needs. Thus, separate channels are set up for each of the users. Because of this approach, air interface traffic in the wireless network is significantly impacted. For example, the number of users per cell significantly decreases with every high bandwidth video connection, leaving limited support for multiple video connections. Because separate channels are set up for each of the users, identical high bandwidth channels transmitted to multiple destinations are often used, which requires significant wireless network resources. The above-described individual unicast transmissions to each user are too inefficient and do not take advantage of the efficiencies of multicasting.
Multicasting provides improvements over the multi-path unicast approach, but typical multicasting is still inefficient. For example, a separate multicast connection will exist for each profile, even though the same media content is sent.
Additionally, users sharing a multicast connection cannot change their service/Quality of Service (QoS) profile, e.g., picture quality, in real time without disconnecting from the current active connection. Also, users cannot easily compensate for traffic impairments on a multicast connection. Moreover, due to high bandwidth demand, handoff is cumbersome and difficult, e.g., an adjacent sector may not have the required bandwidth. Likewise, joining and leaving a multicast wireless group is difficult to implement.